Manufacture of thread or the like



Jam 19, 1943- A. H. BURKHQLDER 2,309,072

MANUFACTURE OF THREAD OR THE LIKE Filed July 29, 1940 3 Sheets-Sheet l Gttorneg Jan. 19, 1943. A. H. BURKHOLDER MANUFACTURE OF THREAD OR THE LIKE Filed July 29, 1940 5 Sheets-Sheet 2 ALBEN H. EURKHOLDER Gttorncg Jan. 19, 1943. A. H. BURKHOLDER- 2,309,072

MANUFACTURE OF THREAD OR THE LIKEy 5EWER @mmm Patented Jan. 19, y194i?.

. MANFACTURE .OF THREAD R LIKE Alden n. Burkholder, cleveland, ohio, assignmto Industrial Rayon Corporation, Cleveland, Ohio, a corporation of Delaware f Application July 29, 1940, serial No. 348,106

. 4 Claims.

, This invention relates to the manufacture of filaments, threads, cords, ribbons and other forms of strand material, all of which are referred to hereinafter by the generic term fthread.

The invention may bev employed to especial advantage in the manufacture of artificial silk thread formed by the extrusion of a coagulable spinning mass into a suitable coagulating liquid. For purposes of illustration, but not in any sense vof limitation, the features of novelty characterizing the'invention will be described in connection with the manufacture of multiple lament viscose artificial silk thread on :apparatus generally similar to that shown, described and claimed in copending application Serial No. 7,114 (Patent 2,225,642), filed February 18, 1935, by Walter F. Knebusch and Alden H. Burkholder. It will, however, be appreciated that the invention may be employed in the f nanufacture on other types of apparatus of sundry Vother kinds f of thread, whether of natural or synthetic origin.

Briey, the invention relates to the sequence of the operationsl performed upon the thread, to the conditions of processing, and to certain novel methods of maintaining the desired characteristics in the processing media.

In the drawings, Figure 1 represents a cross section from line "I-I of Figure 2 of a'portion of a machine for the manufacture of viscose artificial silk thread similar to that of said application. Figure `2 is a side elevation, from line 2-2 of Figurel, of the portion ofthe machine illustrated in Figure 1. Figure 3 is a flow diagram of the circulation system for the coagulating liquid employed in said machine. Figure 4 is a flow diagram of the circulation system for the processing liquid applied to the thread short- 'ly after its coagulation. Figure 5 is a similar flow diagram of the circulation system for the processing liquid next applied to the thread.

As indicated in Figures 1 and 2, each thread I is formed by the extrusion of viscose through a spinneret 2 into a coagulating bath 3 contained in trough 4. The viscose is supplied to each spinneret 2 by a mass tube 5 through which the.

viscose is forced by suitable means, such as a gear Ipump 6 associated with a viscose supply in series, although more or less ythan five may v be employed.

Each of saidthre'ad-advancing reels 8 to I2,

inclusive, is adapted, during rotation, to store a yof the reel.l

long lengthof thread continuously but temporarily in a' largenumber of closely spaced', generally helical turns which are advanced progressively from the supported to the unsupported end The thread-supporting surface of each reel consists of a plurality of circumferentially spaced, axially extending bars which cooperate to advance the thread in the manner stated, the illustrated reel being in general of the type described in said application Serial No. 7,114. The reels shown in the drawings of the present application are `in semi-diagrammatic representation, the indicated spacing of thread turnsy being considerably greater than the spacactually employed in the ment, not only are the reels readily accessible for operating purposes but the thread can pass directly from reel to reel without undergoing detrimental bending or guide stresses.

Inthe apparatus illustrated, a plurality of such descending series of reels is disposed on\e,ach side pipe I common to all pumps 6 on the same side of the machine. When the viscose comes into contact with the coagulating bath, a solidified thread I is formed which may be and preferably 'of a common longitudinallyv extending coagulating trough-4. As shown' in Figure 1, the banks of reels,- when viewed in transverse cross section, resemble an inverted ,V..`Corresponding reels of .all downwardly extending series on each side of the machine .are disposed in rows extending lengthwise of the machine, which makes possible the supply and removal of processing liquids by .means of common longitudinally extending conduits on each side of the apparatus. It also provides various other practical advantages, such as construction economies.

After being withdrawn from the coagulating bath, eachthread I is advanced from the supported to the unsupported end of one of the reels 8, being discharged from the reel beyond the lateral edge of trough 4. In the illustrated embodiment of theinvention, no processing lliquid is applied to the thread on reel 8; instead. a

period for furthering the coagulation of the thread is provided by storing a relatively long length of thread on said reel before the thread is subjected to processing liquid on succeeding reels 9 to I2, inclusive. As the thread I passes from reel 8 to the supported end of reel 9, it proceeds vertically downward through a channel I4 associated with the longitudinally extend side of coagulating trough 4.

n the reels subsequent to reel 8, liquid is applied to the thread by means of a reagent tube I5 communicating with a conduit I6 which extends longitudinally of the machine. Said conduit I6 supplies all corresponding processing reels on one side of the apparatus. A longitudinally extending collecting trough I1 which communicates with the sewer or with suitable recirculation means extends lengthwise of the machine beneath each such horizontal series of reels. In the embodiment of the invention illustrated, conduits I6 for reels I0 to I2, inclusive, are formed integrally with the collecting troughs Il above such reels.

It is desirable that each of the reels on which liquid is applied to the thread shall be so operated that a iilm of processing liquid extending entirely around and for substantially the length of its thread-bearingperiphery is formed upon the reel. In the illustrated apparatus, the turns of thread on each of reels 9 to I2, inclusive, are spaced suliiciently close together to permit the processing liquid which is applied to the thread to form such a film. The reel is preferably rotated at a speed such that the centrifugal force which is developed helps 'to maintain the iilm. Liquid is applied to the unsupported end of the lreel, which is'elevated slightly above the supported end so that countercurrent flow is obtained: Under such conditions, the formation upon the reel of the lm of processing liquid is promoted.

As previously mentioned, each thread I is formed by extrusion of viscose into a bath containing dilute sulfuric acid, after which it is stored on reel 8 invorder to permit coagulation of the thread to proceed. Thereafter, the thread is subjected on reel 9 to a somewhat more dilute sulfuricacid solution, preferably heated, and on reel I0 to a `still more dilute sulfuric acid solution. The latter need not necessarily be heated, but can advantageously be heated to a temperature somewhat lower than that of the liquid applied on reel 9. Preferably, the acidity of the liquid applied on reel IIJ isso low that it does not cause deleterious effects when the thread is subsequently subjected on reel II to an alkaline desulfurizing medium such as dilutev sodium sul-,- fide. after which it may be subjected to other processing operations on subsequent reels.

In Figure 3 is shown the coagulating liquid circulation system employed in connection with the illustrated apparatus.

In such system, coagulating liquid is pumped through pipe I8 to a header box I9 disposed above the level of the coagulating liquid in trough 4. From header box I9. which is pro- The thread may be washed on reel I2,

vided with an emergency overow pipe 2|, the I coagulating liquid flows into the coagulating trough 4 through pipes 22 extending longitudinally of the trough (Figure 1). The coagulating liquid is drained from said trough ,4 through a plurality of upright pipes 23 communicating with a common drain pipe 24 which pipes 23 are disposed at spaced intervals lengthwise of the trough: The inlets to such pipes 23 are disposed at a predetermined distance above the bottom of trough I in order to maintain the coagulating bath 3iat the desired level.

The coagulating liquid draining from trough 4 through pipes 23 and 24 passes to make-up tank 25, but only after a portion of the circulating coagulating liquid has been bled ofi from the system through pipe 26 in order to maintain the volume of liquid in the system constant.

The reagents needed to rejuvenate the coagulating liquid are added in make-up tank 25. Thus sulfuric acid from tank 21 may be added through pipe 28, water, if needed, from tank 29 through pipe 3|, and zinc sulfate from tank 32 through pipe 33. -Provision may also be made for adding sodium sulfate, if required. The replenished liquid is shown as passing through conduit 34 into a storage tank 35 in which a substantial part of the impurities present in the coagulating bath agglomerateto form a sludge readily separable from the coagulating liquid.

- coagulating liquid which is relatively free from sludge overflows a partition 38 in said tank into a compartment 31 in which an oleaginous material such as mineral oil emulsied in Water by means of a suitable emulsifying agent, such as a sodium salt of a sulfonated higher hydrocarbon, is added to and mixed with the coagulating.

liquid. The purpose of adding the emulsiiied mineral oil, as from tank 38, is to render innocuous the relatively large quantity of insoluble impurities in the coagulating liquid; e. g., the sulfur formed in the regeneration reaction, and

also to make possible thel removal of such im purities from the coagulating liquid by forming -the sludge to' which reference has been made.

The liquid in compartment 3l is forced by pump 39 through pipe I8 into coagulating trough 4, as indicated above.

In order to obviate the necessity of adding sodium sulfate to the system, some of the coagulating liquid is concentrated by passing it through an evaporator. To that end, a coagulating liquid evaporator 40 of the usual type is employed, its inlet being connected through pipe 4I with supply pipe I8. Its outlet is connected through pipe 42 with discharge pipe 24 from the coagulating trough 4. By means of such a system, a portion of the water in the coagulating liquid can be continuously removed; consequently, the concentration of acid, sodium sulfate, and other desired substances in the portion of the coagulating liquid returned to the system from the evaporator can be increased so as to maintain without additions the desired concentration of sodium sulfate in the circulating coagulating liquid. f

The circulation system for the coagulate liquid itself forms no part of the present inventio'n, being claimed in copending application Serial No. 348,232, filed July 29, 1940, by Hayden B. Kline et al. y

The system for circulating the liquid to which the thread is subjected on reel 9 is shown diagrammatically in Figure 4. In said system, liquid is forced upward by means of pump 44 from storage tank 43 through pipe 45 to a headerbox 4B. Said header box is so constructed that the liquid level therein is maintained at a predetermined distance above the `discharge orifices of Y the reagent tubes I5 for the reels 9 disposed system through pipe 52.

' .tions have been made.

through each of reagent tubes I5. More liquid 'header box 46 through pipe 41 and conduits I6:

The excess passes out through overflow pipe 48.

The overflow passed through pipe 48 and the' liquid vcollected in troughs I1 beneath reelsl 9 land removed by means of pipe 49 are intermingledY and passed to make-up tank 50, from which the mixture passes through pipe I to need be added to the system. The amount, of sulfurie acid, sodium sulfate and zinc sulfate carried over bythe thread from the coagulating bath is more than suflicient to maintain the'desired concentration of these substances in the processing liquid employed on reels 9. In time, they-y tend to build up to av concentration considerably greater than that desired; accordingly, a` portion of the processing liquid is continuously bled from the For reasons of economy, the liquid so bled on" is liquid to which no new addi- To that end, pipe -52 communicates with a firstv compartment 53 in makelup tank 50 containing only contaminated liquidpassing to it from reels 9.

A In order to replace the volume of liquid sobled off from the system, fresh water is added to makeup tank 50 through pipe 5,4 from any suitable source,- such as tank 55. Said pipe 54|v discharges into `a second compartment 56 in make-up tank 5i] `in such manner that it does not intermixwith theliquid bled o'if from the system. In this manner, both the acid concentration and the quantity optimum value, which, as will appear hereinafter, is approximately 5%.

In the preferred embodiment of the invention, a

soluble oil; e. g., a sodium or potassium salt of a sulfonated hydrocarbon, such as Twitchell oil, is added to the circulationA system for reasons later Vto be indicated. Such oil is supplied from tank 51 through pipev58, which also discharges into compartment- 55. In order to obtain an efficient dissemination of the oil in the circulating liquid, means are provided for mixing the soluble oil and the Water supplied to the system in agcontainerV 59 in make-up tank' 50 from which the mixed liquid overflows into compartment56. Preferably, the'water added in container 59 is hot water.

Ordinarily, a thorough intermixing of the soluble oil and the added water occurs before and as the mixture passes from container 59 into compartment 56 of make-up tank 50.

age tank 43, but could, if desired, be located in lcompartment'. 56 or 6I of make-up tank y5l). L

The circulation system for the processing liquid applied to the thread on reels I0 is similarly arranged, as is evident from Figure 5. The liquid is supplied by means of a pump 63 from storage tank 64 through pipe 65 to a header box 66. From said header box, vthe processngliquid passes through The liquidl overowing from compartment 56 into still a third pipe 61 to conduits I6 supplying reagent distributors I5 for reels I0. From collecting troughs I'I on opposite sides of the apparatus, the collected processing liquid passes through pipe 68 to a make-up tank v69. Overilow pipe 1I by,l means of which a predetermined level of liquid is maintained in header box 66 also communicates with vmake-up tank 69, from which the liquid passes throughpipe I2 back to storage tank 64.

Apart from the materials carried by the thread from the preceding processing stage, no substance other than water is added to the circulation system for the processing liquid applied tothe thread on reels I0. Because the amount of.I acid and other ingredients carried over by the thread would in time reach a concentration much greater. than that desired, a portion of the liquid inthe system is bled therefrom through .pipe 13. Inthe` arrangement illustrated in Figure 5, pipe .13 communicates with pipe 66 containing the contaminatedhquid passing from thecollecting troughs II beneath reels I0, wherefore only the contaminated liquid is withdrawn fromfthe system.

on the reel I I, as well as other processing liquids applied on succeeding reels,fmay be similarly recirculated by systems including means for bleeding ofi' contaminated liquids'and' adding fresh reagents. A

In the operation of the illustrativeapparatus herein described, viscose is lextruded into a coagulating bath containing by weight approximately 10.75% lsulfuric acid, approximately 20% sodium sulfate, approximately 0.37% zinc in the form of zinc sulfate, and from 0.6 to 0.9% emulsiedvmineral oil, the bath in the vicinity of the spinnerets being maintained at a temperature of approximately C. Threads of 150 denier, 40 laments, are formed by extrusion of the viscose through the spinnerets, each such thread being drawn upward by av correspondinglyA disposed reel 8 located above the coagulating bath. Such reel, which is so constructed that it advances the thread lengthwise thereof .for a vdistance of 4 inches in a helix 5v inchesin diameter' having 1l turns to the inch, rotates at a. speed of 154 R. P. M. I

From reel 8, the thread is passed downward tosucceeding reel 9, which is 5 inches in diam-` eter but which rotates at a speed of 169 R. P. M.

This increase in peripheral speed imparts aV stretchof approximately 10% to the thread between reels 8 and 9. "Ihe'thread is stored on reel 9 in a helix about 4 inches long having 19 turns per inch. The liquid applied to the thread on the reel contains approximately 2.5% lsulfurie acid, approximately 5% of sodium sulfate,

approximately .07% of zinc as zinc sulfate, and

about .5% of Twitchell oil, which is composed of about 10% to 15% sulfonated mineral oil mixed with plain mineral oil. The liquid is applied at'a rate of 340 cc. per minute to the thread on each reel 9, being applied at al temperature of about C. y

The processing vliquid for reels 9 is recirculatedby the system shown in Figure 4. The

.05% sodium hydroxide.

yonly liquids added to the circulation `system are fresh hot water and Twitchell oil, which is added vat the rate of 4 grams per thread r hour. The remainder of the ingredients in e liquid are supplied from the liquid carried by the ,thread passing from the coagulating bath into the treating stage comprising reel 9, wherefore they have substantially the same proportions with respect to each other as they have in the coagulating bath. The processing liquid applied to the thread in this manner serves to harden it preparatory to the perfomance of subsequent processing o rationson it.

p'fl'he threadthen passes to reel l0, which is a. 5-inch reel rotating at the same speed as preceding reel 9. The turns of thread on this reel are disposed in a helix the pitch of which is23 turns per inch. AProcessing liquid contain-,- ing from .015% to .025% of sulfuric acid, from .03% to .05% of sodium sulfate, traces of zinc in the form of zinc sulfate, and small quantities of Twitchell oil is applied to the thread on reels i0. 'I'he ingredients other than water are present in substantially the same ratio as in the liquid applied to the thread on reel 9, since such ingredients are carried over by the thread. On reels I0, the liquid is applied tothe thread at the rate of 240 cc. per minute at a temperature of 30 C. f

On reel Il', a desulfurizing medium consisting ofsa dilute alkaline solution ofv sod1um sulfide is applied to the thread, the .reel being ofthe with coagulatlng liquid.

same dimensions, rotating at the same speed,

and advancing the thread in a helix of substantially the same pitch as in reel i0. The solution contains' from .3% to sciumlsilde- 1inlclit,

ose of stabil ng e so u ion, a o

for the purp It is applied to the thread on the reel at a temperature of approximately C. at a rate of 240 cc. per minute.

The above-described system of processing possesses numerous unusual advantages, particularly inthe manufacture of viscose artificial silk thread by a continuous process.

In the manufacture of such thread, regeneration of the cellulose content of viscose does not occur instantaneously.' Apparently the viscose rst solidifies without, undergoing complete chemical reaction; that is, the material of which the/thread is first constituted is in part a solidied form of cellulose xanthate. Thereafter the cellulose of which the thread is ultimately formed is regenerated, the sodium of the sodium cellulose xanthate of the viscose forming 'sodium sulfate by reaction with the sulfuric acid and the sulfur going' into such by-products as carbon disulfide, hydrogen sulilde, and elemental sulfur. The entire reactionrequires an appreciable time for its completion: Of the two eiects, the solidication proceeds rapidly but regeneration more slowly, probably because it must proceed from the exterior to the interior of eachiament.

In the illustrated embodiment ofthe invention, the indicated substantially vertical withdrawal of the thread from the coagulating bath by means of reel 8 causes a column of coagulating liquid to adhere to and to rise with the thread. In eiect, this adds considerably to the immersion length of the thread in the coagulating bath, which length is approximately `15 inches. The liquid is largely, but not entirely, stripped from the thread by guide "I8, sufcient liquid being carried beyond said guide .so that In the thread starting on reel 8. the cellulose content is apparently only incompletely regenerated, but because of the presence of the liquid carried up by the thread, regeneration proceeds on the reel. The thread is stored on the reel for a period long enough to permit further regeneration to take place; in addition, a decided change in the color of the thread from dark to light yellow occurs while the thread s stored on the reel. Regeneration of the thread, although occur-l ring in considerable measure, is apparently not completed on reel 8: Asa result, the thread by the time it leaves the reel is probably fully solidiiled but not completely regenerated.

As it passes downward to succeeding reel 9, the thread is stretched by any desired amount, within reasonable limits, while still in a more or less plastic condition. Conveniently, such stretch may be of the order of about 10 per cent. In the' apparatus illustrated, such stretch is comparatively gradual in that it takes place in a length of thread passing through air for a distance of several feet. In the illustrated embodiment ot the invention, this length o f thread; viz., the distance from reel 8 to reel 9, is-between six and seven feet. Gradual stretching of the thread in this manner; i. e., after it is substantially completely solidilied, while it is at least partly and preferably more than one-half regenerated, but before it is regenerated completely and `under conditions such that the stretch cannot carry back to the extremely soft thread issuing from the spinneret, has been found to be particularly advantageous.

Among other things; such stretching considerably increases the tensile strength of the thread without, however, substantially increasing the tendency of the thread to shrink upon drying. This is probably due to the fact that the stretching of the'thread is performed a suicient length of time after extrusion* to permit the micellar structurev of the l)zellulose to form but before a su'icient length of time `has elapsed to permit the thread to harden to an extent such that i Although the thread starting on reel 9 is believed to be completely solidified, its cellulose content is, as indicated, but incompletely regenerated. Subjecting the incompletely regenerated thread to the action of a hot dilute acid Von reel 9 results in substantial completion of the regeneration of the cellulose on this reel, permanently setting the stretch in the thread; that is, such thread will, upon being rewet after having been dried, shrink much less lthan thread which has been stretched after having been completely vregenerated. i

Because regeneration of the cellulose is substantially, if not entirely, completed on reel 9, sulfur and other substances formed as by-products of the regeneration reaction tend to deposit in the form of hard incrustations on said reel.

Such incrustations have been' found to damage the thread, principally by breaking the illaments thereof; The addition of a suitable oily material has been found to inhibit the deposition of such asoaova Where such a material is used, the processing liquid applied vto the thread on the reel washes away the by-'products, such assulfur, produced as a result'of the regeneration reaction. Moreover, the added material serves to lubricate the thread and thereby reduce friction of the thread not only on reel 9 but also on succeeding reels.

A suitable soluble sulfonated hydrocarbon such as Twitchell oil serves to reduce the surface tensionof the liquid in which it is dissolved, wherefore the formation of the previously mentioned lm of processing liquid between adjacent turns or thread n reei -s is faeiutaa. The thread turns may. therefore, be considerably more widely spaced on reel 9 than on other reels without'concomitant disruption of the film. 'I'his is advantageous because a lwider spacing of the thread .turns is needed on reel 9 in consequence ofthe incomplete regeneration, and hence larger diameters, of the thread illaments. Moreover, reduction of the surface tension ofthe processing liquid reduces the surface tension of the lm between the bars of the reel which are retracted during the thread advancing operation and the turns of thread on the reel, thus preventing breakage of the film and henceA breakage of the thread lament.A

'I'he primary purposegof employing the acidic processing liquid applied tothe thread on reel I0 is to wash the thread before it is desuliurized. However, maintenance in a mildly acid state of the liquid applied to the thread on reel I0 leadvantageous in that it tends to prevent the formation of insoluble zinc deposits in such liquid and on the thread, doing so by maintaining the zinc in the form oi relatively soluble salts which are readily removed by the washing operation. The

degree of acidity is preferablyso slight as not to l cause diillculty in the succeeding alkaline desulfurizing stage.

The examples'of thread processing conditions given above are purely illustrative and may be modified considerably, although the described conditions are preferred for th indicated kind and size of thread..

In the case of the liquid employed-as the coagulant in coagulating bath .3, not only the concencient results with maximumeconcmy.

The remarks made above in connection wit the processing of the thread on reel 9 apply with equal force to the processing of the thread on the succeeding reel vI 0. Thus the temperature of the liquid applied on such reel may vary considerably, as from 20 C. to 60 C. The acid concentration in the liquid applied to the thread on this reel may vary from .015% to as high as .5% or more, the upper limit being in general deter- .mined by the possibility of formation of undesirable precipitates if the thread is subjected to an alkaline treatment in the. succeeding stage.

Other modifications may be made in the processing conditions and sequence of processing operations, as well as in the apparatus illustrated, without departing from the spirit of the invention. For example, while a stretch of about 10% has been indicated as being imparted to the thread between reels 8 and 9, either a greater or lesser stretch or even none at all, may be imparted to the thread. Further, while the illustrated examples have been discussed in connection with the supplying of treating ingredients to later treating stages by a liquid carried by the thread from earlier treating stages, it is apparof thread and yeven to the manufacture of thread by discontinuous methods.

4It is intended that the patent shall cover, by suitable expression in the appended claims, whatever features of patentable novelty reside in the invention.

What is claimed is:

1.- A continuous process of manufacturing multiple filament viscose artiiiciallsilk thread comprising the sequentially performed steps oi' forming the thread by extruding viscose into a coagulating bath having an acid concentration l substantially maintained at a predetermined tration but also the temperature of'the coagulat- A ing bath may vary considerably from `that indicated, as from approximately 8% to approximately 14% in the concentra-tion of the acid and from 30 C. to 50 C. in temperature. Under some circumstances, .the coagulating bath need not be heated at all. With changes in acid concentration, appropriate changes should be made in the concentrations. of the other ingredients in the coagulating bath; i. e.. the sodium sulfate and zinc sulfate, all as well understood in the art.

In the case of the processing liquid applied to the thread onreel 9, the acid concentration may range from 1% to 5% and the temperature from 50 C. to 80 C., although these are not limitative.

In general, `it is found, that the use of a high temperature will permit the use of lower acid concentrations. The concentrations of the other constituents of the liquid applied to the 4thread on this reel should be .varied with the acid concentration. If, however, the liquid carried over by the thread supplies all of such constituents, the proportions will naturally be very nearly the same as those in the liquid carried over from the coagulating bath.

The amount of any 10-15% base Twitchell oil which it may bevdesired to add may vary from .3% to 1% or. more, although a concentration termined value between 0.015%

vvalue between 8% and 14%; stretching the incompletely regenerated thread by an-amount of the order of 10%; subjecting the thread to the action of a first processing liquid characterzedby an acid concentration substantially maintained at a predetermined value between 1% and 5%;

subjecting the thread to the action of a second processing liquid characterized by an acid concentration substantially 'maintained at a predeand 0.5%; and drying the thread.

2. A continuous process of manufacturing multiple filament viscose articial silk -thread 'comprlsing the sequentially performed steps of forming the thread by extruding viscose into a coagulating bath having an acid concentration substantially maintained at a predetermined value between 8% and 14%; stretching the incompletely regenerated thread; subjecting the thread to the action of a first processing liquid characterized by an acid concentration substantially maintained at a predetermined value between 1% and 5%; subjecting the thread to the action of aiseeond processing liquid characterized by an acid concentration substantially maintained at a predetermined value between 0.015% and 0.5%; land drying the thread.

3. A continuous process of manufacturing mulprising the sequentially performed steps of forming the thread by extruding viscose into a coagulating bath at a temperature between 30 and 50 C. having an acid concentration substantially maintained at a predetermined value between 1 8% and 14%; subjecting the thread to the action multiple iiiament viscose articial silk thread Atiple illament viscose articial silk thread comcomprising the sequentially performed steps of forming the thread by extruding viscose into a coagulating bath having an acid concentration substantially maintained at a predetermined value between 8% and'14%: stretchingthe incompletely regenerated thread by an amount of the order of 10%; subjecting the thread to the action of a. rst processing liquid at a temperature between 50 and 80 C. characterized by an acid concentration substantially maintained at a predetermined value between 1% and 5%; sub- Jecting the thread to the action of a second processing liquid at a temperature between 20 and 60 C. characterized by an acid concentration substantially maintained at a predetermined :gaud between 0.015% and 0.5%; and drying the ALBEN H. BURKHOLDER. 

